various branches, each branch having a current of its own taken from the main circuit. In parallel circuits it is not necessary that current flow in each branch to have current flowing the main circuit. In a parallel connection of lights, one light may be burnt out but still the other lights would light. In a series connection of lights, if one is burnt out, the whole circuit is dead.
Now let us take the parts used in Fig. 10 and connect them in parallel. See Fig. 11 which shows how this parallel circuit would look. You can trace through this circuit and follow the current as it flows from the battery, starting either at the negative pole or the positive pole, it doesn’t make any difference. Some of the current will flow through R1, some through R2, and some through R3. If R1 were broken, current would still flow through R2 and R3, as can easily be seen. But with R1, R2, and R3 in the circuit, will the total resistance be R1 + R2 + R3? Not at all. In fact, the more resistances we have in parallel, the more current will flow through the main circuit A and B.
Fig. 11
The total resistance in the circuit will be considerably less than the sum of the three resistances because the current has more paths to travel over than if the resistances were connected in series.
The water system shown in Fig. 12 will help to make clear the action of loads in parallel. The branches marked T correspond with the resistances in our former example. Notice that the branches are pipes of smaller diameter than the main pipe and so can really be called water resistances. But as these are connected in parallel as shown, altogether they will not offer much resistance to water flow. If there were only one it might hold back the water considerably. But as there are four in parallel, there are four paths for the water to flow through which it manages to do very easily.
Now returning to Fig. 11, trace through it again. It is apparent that the same amount of current won’t flow through every point in that circuit. It divides between the branches and
